Compressed air energy storage system coupled with waste heat of thermal power plant and control method thereof

Abstract

The invention relates to the technical field of compressed air energy storage, and discloses a compressed air energy storage system coupled with waste heat of a thermal power plant and a control method thereof, and the compressed air energy storage system comprises an energy storage unit, a turbine unit, a first heat exchange unit and a second heat exchange unit, the first heat exchange unit comprises a first heat exchanger, at least one second heat exchanger, a first storage device and a second storage device, and a fourth flow path is arranged on the upstream side of the at least one turbine structure, so that the second heat exchanger is used for heating airflow on the upstream side of the at least one turbine structure; the second heat exchange unit comprises a third heat exchanger, a fourth heat exchanger, a third storage device and a fourth storage device; an eighth flow path of the fourth heat exchanger is suitable for circulating a waste heat medium of the thermal power plant. Therefore, the waste heat of the thermal power plant can be recycled and utilized, meanwhile, part of energy of compressed air can be utilized to improve the generating capacity of the turbine unit, the turbine process is not prone to being limited by the compression process, and the waste heat can be utilized at any time when needed.

Description

Technical Field

[0001] The present invention relates to the technical field of compressed air energy storage, and in particular to a compressed air energy storage system coupled with waste heat of a thermal power plant and a control method thereof. Background Art

[0002] Compressed air energy storage refers to a storage method that uses electricity to compress air during the low load period of the power grid, and releases compressed air to drive the steam turbine to generate electricity during the peak load period of the power grid. As a new energy storage technology, it has received high attention from both inside and outside the industry in recent years and has developed very rapidly. Coupling with other flexible resources and improving efficiency are the future development directions of compressed air energy storage.

[0003] For this reason, there is room for improvement in the coupling arrangement with compressed air energy storage. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a compressed air energy storage system coupled with waste heat from a thermal power plant, which can recover and utilize waste heat from the thermal power plant, and can also utilize part of the energy of the compressed air to increase the power generation of the turbine unit, and make the turbine process less susceptible to the restrictions of the compression process, so that it can be used at any time when needed, thereby improving the operational flexibility of the compressed air energy storage system.

[0005] The present invention also provides a control method for a compressed air energy storage system.

[0006] According to the first aspect of the present invention, a compressed air energy storage system coupled with waste heat from a thermal power plant comprises: an energy storage unit, the energy storage unit comprising a compression device and an air storage device, the air storage device being connected to the outlet side of the compression device; a turbine unit, the turbine unit being connected to the outlet side of the air storage device and comprising a plurality of turbine structures; a first heat exchange unit, the first heat exchange unit comprising a first heat exchanger, at least one second heat exchanger, a first storage device and a second storage device, the first heat exchanger comprising a first flow path and a second flow path for mutual heat exchange, the first flow path being respectively connected to the first storage device and the second storage device, the second flow path being respectively connected to the compression device and the air storage device, the second heat exchanger comprising a third flow path and a fourth flow path for mutual heat exchange, the third flow path being respectively connected to the first storage device and the second storage device The fourth flow path is provided on the upstream side of at least one of the turbine structures so that the second heat exchanger is used to heat the airflow on the upstream side of the at least one turbine structure; the second heat exchange unit, the second heat exchange unit includes a third heat exchanger, a fourth heat exchanger, a third storage device and a fourth storage device, the third heat exchanger includes a fifth flow path and a sixth flow path for mutual heat exchange, the fifth flow path is respectively connected to the third storage device and the fourth storage device, the sixth flow path is respectively connected to the gas storage device and the turbine unit, so that the third heat exchanger is used to heat the airflow between the gas storage device and the turbine unit, the fourth heat exchanger includes a seventh flow path and an eighth flow path for mutual heat exchange, the seventh flow path is respectively connected to the third storage device and the fourth storage device, and the eighth flow path is suitable for circulating waste heat medium of a thermal power plant.

[0007] According to the compressed air energy storage system of the embodiment of the present invention, a first heat exchange unit is provided to link the compression process with the turbine process, so that the turbine process can utilize part of the energy of the compressed air to increase the power generation of the turbine unit, while taking into account the storage convenience, energy storage density and storage cost of the compressed air; moreover, due to the provision of the first storage device and the second storage device, it is convenient to store part of the energy of the compressed air through the heat exchange medium, thereby improving the independence between the compression process and the turbine process, making the turbine process less susceptible to restrictions by the compression process, so that it can be used at any time when needed, which can improve the operational flexibility of the compressed air energy storage system.

[0008] In some embodiments, a plurality of the turbine structures are arranged in sequence along the air flow direction, and a second heat exchanger is respectively provided on the upstream side of each of the turbine structures.

[0009] In some embodiments, the number of the turbine structures is three or more.

[0010] In some embodiments, the compressed air energy storage system further includes: a switch valve, wherein the switch valve is disposed between the energy storage unit and the turbine unit to control the on-off between the energy storage unit and the turbine unit.

[0011] In some embodiments, the second heat exchange unit further includes a booster, and the booster is used to pressurize the medium in the second heat exchange unit.

[0012] According to the control method of a compressed air energy storage system of an embodiment of the second aspect of the present invention, the compressed air energy storage system is a compressed air energy storage system coupled with waste heat of a thermal power plant according to the above-mentioned first aspect of the present invention, and the compressed air energy storage system has a first working mode and a second working mode. In the first working mode, the energy storage unit and the first heat exchange unit are both operating, the turbine unit is not operating, and the third heat exchanger is not operating; in the second working mode, the energy storage unit, the first heat exchange unit and the turbine unit are all operating, and the third heat exchanger is operating.

[0013] The control method of the compressed air energy storage system according to the embodiment of the present invention makes it easy for the compressed air energy storage system to adapt to the working conditions of different loads of the power grid, so as to meet the usage requirements of different loads of the power grid.

[0014] In some embodiments, the first storage device and the second storage device contain heat transfer oil, and the third storage device and the fourth storage device contain water. In the second working mode, the temperature of the water in the third storage device is T1, and the temperature of the water in the fourth storage device is T2. The fourth heat exchanger heats the air flow flowing out of the air storage device to a preset temperature T3, T1<T3<T2<100℃.

[0015] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0017] Figure 1 is a schematic diagram of a compressed air energy storage system according to some embodiments of the present invention;

[0018] Figure 2 is a flow chart of a control method for a compressed air energy storage system according to some embodiments of the present invention.

[0019] Reference numerals:

[0020] Compressed air energy storage system 100,

[0021] Energy storage unit 1, compression device 11, gas storage device 12,

[0022] Turbine unit 2, turbine structure 21,

[0023] The first heat exchange unit 3, the first heat exchanger 31, the first flow path 311, the second flow path 312, the second heat exchanger 32, the third flow path 321, the fourth flow path 322, the first storage device 33, the second storage device 34,

[0024] The second heat exchange unit 4 , the third heat exchanger 41 , the fifth flow path 411 , the sixth flow path 412 , the fourth heat exchanger 42 , the seventh flow path 421 , the eighth flow path 422 , the third storage device 43 , and the fourth storage device 44 . DETAILED DESCRIPTION

[0025] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0026] The disclosure below provides many different embodiments or examples to implement different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific processes and examples of materials, but those of ordinary skill in the art can be aware of the applicability of other processes and / or the use of other materials.

[0027] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0028] Below, with reference to the accompanying drawings, a compressed air energy storage system 100 coupled with waste heat from a thermal power plant according to an embodiment of the first aspect of the present invention is provided. It can be understood that the compressed air energy storage system 100 of the embodiment of the present invention can couple the waste heat generated by the thermal power plant during operation to recover and utilize the waste heat, thereby improving energy utilization efficiency.

[0029] like Figure 1As shown, the compressed air energy storage system 100 coupled with the waste heat of a thermal power plant includes an energy storage unit 1, and the energy storage unit 1 includes a compression device 11 and an air storage device 12. The air storage device 12 is connected to the outlet side of the compression device 11, so that the compression device 11 can compress the air and then transport it toward the air storage device 12, and the air storage device 12 can store the air compressed by the compression device 11.

[0030] like Figure 1 As shown, the compressed air energy storage system 100 coupled with the waste heat of a thermal power plant also includes a first heat exchange unit 3, the first heat exchange unit 3 includes a first heat exchanger 31, a first storage device 33 and a second storage device 34, the first heat exchanger 31 includes a first flow path 311 and a second flow path 312 for mutual heat exchange, the first flow path 311 is respectively connected to the first storage device 33 and the second storage device 34, the second flow path 312 is respectively connected to the compression device 11 and the gas storage device 12, then the medium in the first storage device 33 can flow to the second storage device 34 through the first flow path 311, or the medium in the second storage device 34 can flow to the first storage device 33 through the first flow path 311, and at least part of the air compressed by the compression device 11 can flow to the gas storage device 12 through the second flow path 312.

[0031] It can be understood that the first storage device 33 and the second storage device 34 are both used to store the first heat storage medium, one of which is used to store high-temperature medium, and the other is used to store low-temperature medium; it can be seen that the first flow path 311, the first storage device 33, and the second storage device 34 can roughly constitute a medium circuit of the first heat exchange unit 3. Due to the mutual heat exchange between the first flow path 311 and the second flow path 312, the compression device 11 compresses the air and then increases the pressure, and the air temperature increases. The high-temperature air flowing through the second flow path 312 can exchange heat with the medium flowing through the first flow path 311, so that part of the energy of the compressed air can be stored through the medium.

[0032] Take the first storage device 33 for storing high-temperature medium and the second storage device 34 for storing low-temperature medium as an example: the two ends of the first flow path 311 are respectively connected to the inlet of the first storage device 33 and the outlet of the second storage device 34, so that the low-temperature medium in the second storage device 34 can be converted into high-temperature medium after heat exchange with the high-temperature air in the second flow path 312 through the first flow path 311 and flow into the first storage device 33, so that part of the energy of the compressed air is stored in the high-temperature medium, so that the energy of the high-temperature medium in the first storage device 33 can be used at any time when needed, so as to realize part of the energy of the compressed air. recycling and reuse; and because the heat of the high-temperature air is transferred to the low-temperature medium when it flows through the second flow path 312, the high-temperature air is converted into low-temperature air after passing through the first heat exchanger 31, which is beneficial to reduce the heat loss generated during the compression process and improve the system efficiency; furthermore, under low-temperature conditions, the density of the air is greater, and more compressed air can be stored in a unit volume. Under the same volume, the low-temperature compressed air can store more energy, which is beneficial to improve the energy storage density. In addition, under low-temperature conditions, the physical and chemical properties of the compression space are relatively stable, and the insulation requirements are relatively low, which is beneficial to improve storage stability and safety and reduce costs. Of course, in other examples, the first storage device 33 can be used to store low-temperature media, and the second storage device 34 can be used to store high-temperature media. At this time, the two ends of the first flow path 311 are respectively connected to the outlet of the first storage device 33 and the inlet of the second storage device 34.

[0033] In the description of this application, "high temperature", "low temperature", "high pressure" and "low pressure" are relative concepts. It can be seen that the arrangement of the first heat exchanger 31, the first storage device 33 and the second storage device 34 can realize the recovery of energy after air compression, while taking into account the storage convenience, energy storage density and storage cost of compressed air.

[0034] like Figure 1As shown, the compressed air energy storage system 100 coupled with the waste heat of a thermal power plant also includes a turbine unit 2, which is connected to the outlet side of the air storage device 12, and the turbine unit 2 includes a plurality of turbine structures 21. The high-pressure air in the air storage device 12 can flow to the plurality of turbine structures 21, and each turbine structure 21 can convert the energy contained in the air flow into mechanical energy to perform work and generate electricity; it can be seen that the compressed air in the air storage device 12 can flow to the turbine structure 21 to expand and perform work. At this time, the first heat exchange unit 3 also includes at least one second heat exchanger 32, and the second heat exchanger 32 includes a third flow path 321 and a fourth flow path 322 for mutual heat exchange, and the third flow path 321 is respectively connected to the first storage device 33 and the second storage device 34, and the upstream side of at least one turbine structure 21 is provided with a fourth flow path 322, so that the second heat exchanger 32 is used to heat the airflow on the upstream side of at least one turbine structure 21, then the compressed air in the air storage device 12 can flow to the corresponding turbine structure 21 through the fourth flow path 322, and the heat of the medium flowing through the third flow path 321 can be transferred to the compressed air in the fourth flow path 322, so that the compressed air can be heated before flowing to the corresponding turbine structure 21, thereby increasing its temperature, thereby increasing its work and increasing the power generation in the turbine process.

[0035] Take the first storage device 33 for storing high-temperature medium and the second storage device 34 for storing low-temperature medium as an example: the two ends of the third flow path 321 are respectively connected to the outlet of the first storage device 33 and the inlet of the second storage device 34, so that the high-temperature medium in the first storage device 33 can be converted into low-temperature medium after heat exchange with the low-temperature air in the fourth flow path 322 through the third flow path 321 and flow into the second storage device 34, so that the energy stored in the high-temperature medium after compressed air is recovered can be transferred to the low-temperature air flowing to the turbine structure 21, so as to use the energy of the high-temperature medium in the first storage device 33 to heat the air flowing to the turbine structure 21, so as to realize the recovery and reuse of part of the energy of the compressed air, and at the same time, the power generation of the turbine unit 2 can be increased. Of course, in other examples, the first storage device 33 can be used to store low-temperature medium and the second storage device 34 can be used to store high-temperature medium. At this time, the two ends of the third flow path 321 are respectively connected to the inlet of the first storage device 33 and the outlet of the second storage device 34.

[0036] It can be understood that the turbine unit 2 includes a plurality of turbine structures 21, and a fourth flow path 322 is provided on the upstream side of at least one of the plurality of turbine structures 21, so that the compressed air is heated by the medium of the third flow path 321 through the fourth flow path 322 and then flows to the corresponding turbine structure 21; the connection method of the plurality of turbine structures 21 is not specifically limited in the embodiment of the present application, and each turbine structure 21 can use the compressed air to expand and do work, so as to improve the power generation to a certain extent. Then, for all the turbine structures 21 of the turbine unit 2: a fourth flow path 322 is provided on the upstream side of each turbine structure 21, and in this case, there are multiple fourth flow paths 322, and the second heat exchanger 32 can be one or more, for example, in Figure 1 In the example, multiple second heat exchangers 32 are arranged one by one with multiple turbine structures 21; or, the upstream sides of some turbine structures 21 are respectively provided with fourth flow paths 322, and the upstream sides of other turbine structures 21 are not provided with fourth flow paths 322. In this case, there may be one or more fourth flow paths 322, and there may be one or more second heat exchangers 32. A single second heat exchanger 32 may include one fourth flow path 322, or a single second heat exchanger 32 may include multiple fourth flow paths 322.

[0037] It can be seen that the setting of the second heat exchanger 32 can utilize the energy recovered after air compression into the turbine unit 2 to increase the power generation of the turbine unit 2; moreover, the energy storage unit 1 and the turbine unit 2 are independent of each other, and there is no direct connection between the operating states of the two, that is, when the energy storage unit 1 is running, the turbine unit 2 can be running or not running, and similarly, when the turbine unit 2 is running, the energy storage unit 1 can be running or not running. The above setting of the first heat exchange unit 3 can meet the independent operation between the energy storage unit 1 and the turbine unit 2. Regardless of whether one or both of the energy storage unit 1 and the turbine unit 2 are running, the first heat exchange unit 3 can match them to achieve energy recovery and / or reuse. In other words, the first heat exchange unit 3 can achieve flexible coupling between the energy storage unit 1 and the turbine unit 2.

[0038] It can be seen that by setting the first heat exchange unit 3 to connect the compression process with the turbine process, the turbine process can utilize part of the energy of the compressed air to increase the power generation of the turbine unit 2, while taking into account the storage convenience, energy storage density and storage cost of the compressed air; moreover, due to the setting of the first storage device 33 and the second storage device 34, it is convenient to store part of the energy of the compressed air through the heat exchange medium, thereby improving the independence between the compression process and the turbine process, making the turbine process less susceptible to the restriction of the compression process, so that it can be used at any time when needed, which can improve the operating flexibility of the compressed air energy storage system 100.

[0039] Exemplarily, the first heat exchange unit 3 uses heat transfer oil as the heat exchange medium. The heat transfer oil has a high specific heat capacity and good thermal conductivity, and can reduce energy loss in the process of transferring heat. The heat transfer oil can maintain its physical and chemical properties within a wide temperature range. When the heat transfer oil is used for a long time in a high temperature environment, it is not easy to undergo adverse reactions such as oxidation, cracking or coking. It has good thermal stability, which is beneficial to improve the reliability and service life of the system and reduce the maintenance cost and downtime caused by medium deterioration. Moreover, compared with traditional heat transfer media such as water and steam, heat transfer oil can operate at higher temperatures. Under almost normal pressure conditions, heat transfer oil can reach and maintain a higher operating temperature, and the operation is safer, reducing operating risks and reducing equipment requirements. In addition, heat transfer oil has the characteristic of uniform heating, which can ensure that the heated object is heated evenly, avoiding local overheating or uneven temperature problems, and the temperature control of heat transfer oil is also very accurate, which can meet the temperature control requirements of different processes.

[0040] In some embodiments, Figure 1 As shown, the compressed air energy storage system 100 coupled with waste heat from a thermal power plant further includes a second heat exchange unit 4, the second heat exchange unit 4 includes a third heat exchanger 41, a third storage device 43 and a fourth storage device 44, the third heat exchanger 41 includes a fifth flow path 411 and a sixth flow path 412 for mutual heat exchange, the fifth flow path 411 is respectively connected to the third storage device 43 and the fourth storage device 44, the sixth flow path 412 is respectively connected to the air storage device 12 and the turbine unit 2, so that the third heat exchanger 41 is used to heat the airflow between the air storage device 12 and the turbine unit 2, so as to realize the compressed air in Preheating before expansion work is beneficial to further increase the power generation of the turbine unit 2, and the setting of the third heat exchanger 41 facilitates heating the compressed air to a suitable temperature (for example, the third heat exchanger 41 is used to heat the compressed air to 37°C) to improve the stability of the compressed air energy storage system 100 in air treatment in subsequent processes; in other words, the third heat exchanger 41 is beneficial to resist the influence of other factors on the compressed air temperature, so that the compressed air flowing to the first heat exchange unit 3 and the turbine unit 2 has a suitable temperature, thereby improving the operating stability of the compressed air energy storage system 100.

[0041] It can be understood that the third storage device 43 and the fourth storage device 44 are both used to store the second heat storage medium, one of which is used to store high-temperature medium, and the other is used to store low-temperature medium; it can be seen that the fifth flow path 411, the third storage device 43, and the fourth storage device 44 can roughly constitute a medium circuit of the second heat exchange unit 4. Due to the mutual heat exchange between the fifth flow path 411 and the sixth flow path 412, the sixth flow path 412 is located upstream of all fourth flow paths 322, that is, the compressed air flowing out of the air storage device 12 first flows through the sixth flow path 412 to be heated, and then flows to the fourth flow path 322 and the turbine structure 21, and the energy of the medium used to heat the airflow between the air storage device 12 and the turbine unit 2 can be stored in the third storage device 43 or the fourth storage device 44 in advance or in time to heat the compressed air flowing to the turbine unit 2 when needed.

[0042] Taking the third storage device 43 for storing high-temperature medium and the fourth storage device 44 for storing low-temperature medium as an example: the two ends of the fifth flow path 411 are respectively connected to the outlet of the third storage device 43 and the inlet of the fourth storage device 44, so that the high-temperature medium in the third storage device 43 can be converted into low-temperature medium after heat exchange with the low-temperature air in the sixth flow path 412 through the fifth flow path 411 and flow into the fourth storage device 44, while the air in the sixth flow path 412 is heated and the temperature is increased, thereby achieving preheating before expansion.

[0043] like Figure 1 As shown, the second heat exchange unit 4 also includes a fourth heat exchanger 42, and the fourth heat exchanger 42 includes a seventh flow path 421 and an eighth flow path 422 for mutual heat exchange, and the seventh flow path 421 is connected to the third storage device 43 and the fourth storage device 44 respectively, and the eighth flow path 422 is suitable for circulating the waste heat medium of the thermal power plant, then the low-temperature medium can pass through the seventh flow path 421 to exchange heat with the waste heat medium of the thermal power plant in the eighth flow path 422, so as to recover the waste heat of the waste heat medium of the thermal power plant, convert it into a high-temperature medium, and store it, so as to heat the compressed air flowing to the turbine unit 2 when needed. Therefore, the fourth heat exchanger 42 can recover the heat of the waste heat medium of the thermal power plant to the third storage device 43 or the fourth storage device 44.

[0044] Generally, during the compressed air energy storage gas injection process, the temperature of the gas storage device gradually rises, and after the gas injection is completed, the temperature of the gas storage device is generally less than 90°C; during the gas discharge process, the temperature of the gas storage device gradually decreases, and may drop to 0°C or below. If the high-temperature heat transfer oil stored in the compression process is used to heat the inlet air of the gas storage reservoir, the overall intake temperature of the turbine will be reduced, thereby reducing the working capacity. Therefore, in the above scheme of the present application, the waste heat of the waste heat medium of the thermal power plant (for example, flue gas is about 130°C, which varies slightly from thermal power plant to thermal power plant) is used to heat the outlet air of the gas storage device 12, so that the outlet temperature of the third heat exchanger 41 is increased to a constant value to increase the turbine inlet temperature.

[0045] In some embodiments, Figure 1 As shown, multiple turbine structures 21 are arranged in sequence along the air flow direction, and a second heat exchanger 32 is provided on the upstream side of each turbine structure 21. At this time, multiple turbine structures 21 are arranged in series, and the compressed air flowing out of the air storage device 12 can flow through the above-mentioned multiple turbine structures 21 in sequence, so as to realize the step-by-step utilization of air pressure energy, which is convenient for reducing the energy loss of a single turbine structure 21 when working under high pressure, reducing energy waste, and improving the efficiency of the overall system.

[0046] In addition, multiple turbine structures 21 are arranged in series, and the configuration and parameters of each turbine structure 21 can be flexibly adjusted according to actual process requirements to adapt to different gas source pressures and temperature adjustments, which is beneficial to improving the applicability of the turbine unit 2 to different working conditions and at the same time facilitates improving the operating stability of the turbine unit 2.

[0047] It can be understood that in the embodiment of the present application, the turbine structure 21 can be two, three, four, five or more than five. Optionally, multiple turbine structures 21 arranged in series can be coaxially connected, so that the energy conversion between the turbine structure 21 and other drive devices is more direct, which is convenient for making the conversion between mechanical energy and mechanical energy not involve the conversion of other energy forms, reducing the loss of energy in the conversion process, which is conducive to improving the energy efficiency ratio of the turbine unit 2; and it is convenient to make the turbine unit 2 compact, save space, and facilitate subsequent maintenance.

[0048] In some embodiments, Figure 1 As shown, there are three or more turbine structures 21, which is beneficial to matching the energy of the compressed air stored in the storage device and achieving better utilization of air energy.

[0049] Combination Figure 1Taking three turbine structures 21 as an example, the three turbine structures 21 are respectively a first-stage turbine structure 21, a second-stage turbine structure 21 and a third-stage turbine structure 21 which are arranged in sequence along the airflow direction. The high-pressure air flowing out of the storage device first enters the first-stage turbine structure 21 to do work. After the pressure is reduced, it enters the second-stage turbine structure 21 to continue to do work. After the pressure is reduced again, it enters the third-stage turbine structure 21 to continue to do work. The next-stage turbine structure 21 makes full use of the residual energy after the expansion of the previous stage to achieve efficient energy conversion.

[0050] Exemplarily, among the three turbine structures 21, a second heat exchanger 32 is provided on the upstream side of each turbine structure 21, so that a fourth flow path 322 is provided on the upstream side of each turbine structure 21, and the high-pressure and low-temperature air flowing out from the storage device first enters the fourth flow path 322 corresponding to the first-stage turbine structure 21 for heat exchange to increase the temperature, and then enters the first-stage turbine structure 21 to do work, the pressure and temperature are reduced, and then enters the fourth flow path 322 corresponding to the second-stage turbine structure 21 for heat exchange to increase the temperature, and then enters the second-stage turbine structure 21 to do work, the pressure and temperature are reduced, and then enters the fourth flow path 322 corresponding to the third-stage turbine structure 21 for heat exchange to increase the temperature, and then enters the third-stage turbine structure 21 to do work.

[0051] In some embodiments, the compressed air energy storage system 100 further includes: a switch valve, which is disposed between the energy storage unit 1 and the turbine unit 2 to control the on-off between the energy storage unit and the turbine unit 2. Thus, it is convenient to control the state of the turbine unit 2 through the switch valve, with a simple structure and convenient operation.

[0052] In some embodiments, the second heat exchange unit 4 also includes a supercharger, which is used to pressurize the medium in the second heat exchange unit 4. For example, the pressure of the medium in the second heat exchange unit 4 is greater than the external atmospheric pressure, so as to appropriately change the phase change temperature of the medium in the second heat exchange unit 4, which is beneficial to prevent the medium in the second heat exchange unit 4 from undergoing phase change during the flow heat exchange process, so as to better recover and store waste heat.

[0053] Exemplarily, the second heat exchange unit 4 uses water as the heat exchange medium. Water has a high thermal conductivity coefficient, which facilitates efficient heat transfer. Water has a large specific heat capacity, that is, water per unit mass can accommodate more heat, so that when water transfers the same amount of heat, less medium mass is required, which is beneficial to improving the overall efficiency of the system. The viscosity of water is relatively low, which means that it has less resistance when flowing in the pipeline and can transfer heat more smoothly. The setting of the supercharger is beneficial to increasing the phase change temperature of the water, so that the water in the second heat exchange unit 4 always remains in a liquid state, so as to better absorb and store waste heat, and the cost is low, with good economy.

[0054] In the description of this application, waste heat medium, also known as residual heat medium, refers to the carrier attached to the heat energy generated and discharged in various production, life or industrial processes and no longer directly used. These waste heat are usually contained in gas, liquid or solid, and are transferred and converted through specific media. Exemplarily, the waste heat medium is the flue gas of the boiler of a thermal power plant, but it is not limited to this.

[0055] According to the control method of the compressed air energy storage system 100 of the second embodiment of the present invention, the compressed air energy storage system 100 is a compressed air energy storage system 100 coupled with waste heat of a thermal power plant according to the first embodiment of the present invention, and the compressed air energy storage system 100 has a first working mode and a second working mode. In the first working mode, the energy storage unit 1 and the first heat exchange unit 3 are both running, and the turbine unit 2 is not running; in the second working mode, the energy storage unit 1, the first heat exchange unit 3 and the turbine unit 2 are all running.

[0056] It can be understood that in the first working mode, the compressed air energy storage system 100 can compress the air, store the compressed air, and recover and store part of the heat of the compressed air. At this time, the operation of the energy storage unit 1 can be understood as the operation of the compression device 11; in the second working mode, the compressed air energy storage system 100 can achieve the purpose of the first working mode, and at the same time, the energy stored in the first heat exchange unit 3 can be used in the turbine unit 2 to heat the air before at least one stage of the turbine process, so as to increase the power generation of the turbine unit 2.

[0057] Exemplarily, when the current grid load is low, the compressed air energy storage system 100 can be switched to the first working mode, in which case the turbine unit 2 does not need to operate to generate electricity, and the air can be compressed and stored in advance; when the current grid load is high, the compressed air energy storage system 100 can be switched to the second working mode, in which case the turbine unit 2 generates electricity to meet the grid load requirements.

[0058] It can be seen that the above-mentioned configuration facilitates the compressed air energy storage system 100 to adapt to the working conditions of different loads of the power grid, so as to meet the usage requirements of different loads of the power grid.

[0059] In some embodiments, the compressed air energy storage system 100 also includes a second heat exchange unit 4, the second heat exchange unit 4 includes a third heat exchanger 41, a fourth heat exchanger 42, a third storage device 43 and a fourth storage device 44, the third heat exchanger 41 includes a fifth flow path 411 and a sixth flow path 412 for mutual heat exchange, the fifth flow path 411 is respectively connected to the third storage device 43 and the fourth storage device 44, the sixth flow path 412 is respectively connected to the gas storage device 12 and the turbine unit 2, so that the third heat exchanger 41 is used to heat the airflow between the gas storage device 12 and the turbine unit 2, the fourth heat exchanger 42 includes a seventh flow path 421 and an eighth flow path 422 for mutual heat exchange, the seventh flow path 421 is respectively connected to the third storage device 43 and the fourth storage device 44, and the eighth flow path 422 is suitable for circulating waste heat medium.

[0060] In the first working mode, the third heat exchanger 41 does not operate; in the second working mode, the third heat exchanger 41 operates. Thus, the second heat exchange unit 4 can be kept consistent with the operating state of the turbine unit 2, so as to achieve preheating before the compressed air flows to the turbine unit 2, thereby increasing the power generation of the turbine process.

[0061] In addition, due to the arrangement of the third storage device 43 and the fourth storage device 44, energy storage can be achieved, and the fourth heat exchanger 42 may or may not be operated in the first working mode, and similarly, the fourth heat exchanger 42 may or may not be operated in the second working mode. Exemplarily, whether the fourth heat exchanger 42 is operated in the first working mode or in the second working mode may depend on whether the waste heat medium of the thermal power plant is introduced into the eighth flow path 422. If the waste heat medium of the thermal power plant is introduced into the eighth flow path 422, the fourth heat exchanger 42 is operated, and the low-temperature medium flows through the seventh flow path 421 to exchange heat with the waste heat medium of the thermal power plant in the eighth flow path 422.

[0062] In some embodiments, the first storage device 33 and the second storage device 34 contain thermal oil, and the third storage device 43 and the fourth storage device 44 contain water, that is, the heat storage medium used by the first heat exchange unit 3 is thermal oil, and the heat storage medium used by the second heat exchange unit 4 is water.

[0063] In the second working mode, the temperature of the water in the third storage device 43 is T1, the temperature of the water in the fourth storage device 44 is T2, and the fourth heat exchanger 42 heats the air flow from the air storage device 12 to a preset temperature T3, T1<T3<T2<100° C. Thus, the water in the second heat exchange unit 4 always keeps liquid flow, so as to improve the stability and safety of system operation.

[0064] Other structures and operations of the compressed air energy storage system 100 according to the embodiment of the present invention are known to ordinary technicians in the field and will not be described in detail here.

[0065] Reference below Figure 1 The compressed air energy storage system 100 according to the embodiment of the present invention is described in detail with a specific embodiment. It is worth noting that the following description is only an exemplary description and is not a specific limitation of the invention.

[0066] like Figure 1 As shown, the compressed air energy storage system 100 includes an energy storage unit 1 , a turbine unit 2 , a first heat exchange unit 3 and a second heat exchange unit 4 .

[0067] The energy storage unit 1 includes a compression device 11 and an air storage device 12. The air storage device 12 is connected to the outlet side of the compression device 11. The turbine unit 2 is connected to the outlet side of the air storage device 12 and includes three turbine structures 21 arranged in sequence along the air flow direction.

[0068] The first heat exchange unit 3 includes a first heat exchanger 31, three second heat exchangers 32, a first storage device 33 and a second storage device 34. The first heat exchanger 31 includes a first flow path 311 and a second flow path 312 for mutual heat exchange. The first flow path 311 is respectively connected to the inlet of the first storage device 33 and the outlet of the second storage device 34, and the second flow path 312 is respectively connected to the outlet side of the compression device 11 and the inlet side of the gas storage device 12. The second heat exchanger 32 includes a third flow path 321 and a fourth flow path 322 for mutual heat exchange. The third flow path 321 is respectively connected to the outlet of the first storage device 33 and the inlet of the second storage device 34. A fourth flow path 322 is respectively provided on the upstream side of each turbine structure 21, so that the second heat exchanger 32 is used to heat the airflow on the upstream side of the corresponding turbine structure 21.

[0069] The second heat exchange unit 4 includes a third heat exchanger 41, a fourth heat exchanger 42, a third storage device 43 and a fourth storage device 44. The third heat exchanger 41 includes a fifth flow path 411 and a sixth flow path 412 for mutual heat exchange. The fifth flow path 411 is respectively connected to the outlet of the third storage device 43 and the inlet of the fourth storage device 44. The sixth flow path 412 is respectively connected to the outlet side of the gas storage device 12 and the fourth flow path 322 corresponding to the first-stage turbine structure 21 along the gas flow direction, so that the third heat exchanger 41 is used to heat the gas flow between the gas storage device 12 and the turbine unit 2. The fourth heat exchanger 42 includes a seventh flow path 421 and an eighth flow path 422 for mutual heat exchange. The seventh flow path 421 is respectively connected to the inlet of the third storage device 43 and the outlet of the fourth storage device 44. The eighth flow path 422 is suitable for circulating waste heat medium, which is the flue gas from the boiler of a thermal power plant.

[0070] The maximum available flue gas of a single unit in a power plant is about 1100t / h, the temperature is 135℃, and the compressed air energy storage gas pressure is 11Mpa; the following takes the example that the flow rate of the boiler flue gas of a thermal power plant to the eighth flow path 422 is 823t / h, the temperature is 135℃, and the temperature flowing out from the eighth flow path 422 is 110℃. The flue gas flowing out from the eighth flow path 422 can enter the smoke exhaust treatment system.

[0071] The first heat exchange unit 3 uses heat transfer oil as the heat storage medium, and the second heat exchange unit 4 uses pressurized water as the heat storage medium. The first storage device 33 is a high-temperature oil storage tank, the second storage device 34 is a low-temperature oil storage tank, the third storage device 43 is a high-temperature water storage tank, and the fourth storage device 44 is a low-temperature water storage tank; wherein, the temperature of the high-temperature water in the third storage device 43 is 52°C, the temperature of the low-temperature water in the fourth storage device 44 is 25°C, and the water flow rate is 254t / h.

[0072] During the compression process, the compressed air is stored in the air storage device 12 through multi-stage compression. The air storage device 12 can be a fixed-volume air storage reservoir; the first heat exchange unit 3 recovers part of the heat of the compression process through heat transfer oil and stores it in the first storage device 33; the second heat exchange unit 4 recovers part of the heat of the waste heat medium through water and stores it in the third storage device 43.

[0073] In the turbine process, the low-temperature air flowing out of the air storage device 12 first passes through the sixth flow path 412 to be heated by the high-temperature water flowing through the fifth flow path 411 to realize the preheating of the compressed air; the preheated air flows in sequence through the fourth flow path 322 corresponding to the first-stage turbine structure 21, the first-stage turbine structure 21, the fourth flow path 322 corresponding to the second-stage turbine structure 21, the second-stage turbine structure 21, the fourth flow path 322 corresponding to the third-stage turbine structure 21, and the third-stage turbine structure 21; in the above process, the third storage device 12 is used to store the compressed air. The high-temperature water in 43 is converted into low-temperature water after heat exchange through the fifth flow path 411 and flows into the fourth storage device 44. The high-temperature heat transfer oil in the first storage device 33 is distributed to three third flow paths 321 (of course, when there are two, four or more third flow paths 321, multiple third flow paths 321 can be arranged in parallel between the first storage device 33 and the second storage device 34) to heat the air flowing in front of the turbine structure 21 respectively. The high-temperature heat transfer oil is converted into low-temperature heat transfer oil after heat exchange and flows into the second storage device 34. Among them, the third heat exchanger 41 is used to heat the compressed air to 37°C.

[0074] Compared with some technologies, many thermal power plants are not equipped with flue gas waste heat recovery devices or have been equipped with flue gas waste heat recovery devices but have not put them into use, resulting in insufficient utilization of the waste heat of flue gas from boilers in thermal power plants. In the embodiment of the present application, the thermal power unit can be coupled with compressed air energy storage on the basis of the existing installed capacity to maximize the utilization rate. At the same time, it can also solve the problems of low-load operation and thermal-electric decoupling faced by the unit at this stage, increase the regulation capacity of the thermal power unit, improve the electrical efficiency of compressed air energy storage, and enhance the utilization of flue gas waste heat in thermal power plants, so as to achieve green and low-carbon power generation and improve the economy of the system. Compressed air energy storage generally has three processes: energy storage (compressed gas injection)-stationary-energy release (turbine gas release), energy release process: consumes heat energy and air potential energy to drive the turbine to generate electricity, and this process generally does not store heat; the heat storage period for waste heat recovery: in principle, it is any period during the energy storage and stationary process of compressed air energy storage. The above-mentioned thermal power plant flue gas recovery and utilization system is applicable to compressed air energy storage power stations: the thermal power plant flue gas waste heat recovery period is the non-compressed air energy storage discharge stage, and the waste heat utilization stage is the compressed air energy storage release (turbine release) stage.

[0075] Among them, the waste heat medium flow rate is: G f，min ≤G f ≤G f，max , waste heat medium temperature: T f，min ≤T f ≤T f，max (limited by the subsequent desulfurization and denitrification process, generally 90°C); the higher the compressed air energy storage efficiency, the more waste heat medium heat recovery is required. Assuming that there is no waste heat recovery link, the efficiency is η0, and the corresponding turbine absorption heat is Q t，0 After adding the waste heat recovery link, the power efficiency is increased to η1, and the corresponding turbine absorption heat is Q t，1 Considering the transformation of the flue gas circuit of a thermal power plant, the waste heat medium flow rate is generally designed to be the total flue gas flow rate G of the power plant f The waste heat medium recovery time is generally considered to be the same as the compressed gas injection time, both of which are t1, considering the upper and lower end difference dT of the heat exchanger L and dT H (generally related to the technical requirements of the heat exchanger), the maximum recovery range of waste heat recovery (waste heat recovery temperature range) is [T f -dT H , T f，min +dT L ], after waste heat recovery, the maximum temperature of the third storage device 43 is T f -dT H , waste heat recovery (or waste heat utilization) Q f，c ≥Q t，1 -Q t，0 ; Point heat exchanger 41 air outlet temperature T 41，out=T 12，out +Q t / C air / G t，air , where Q t The heat required to preheat the air, C air Specific heat of air, G t，air The air flow rate satisfies: sum(Q t )=Q t，1 -Q t，0 ; Waste heat utilization: Q f，c ≥Q f，d =Q t，1 -Q t，0 Among them, the waste heat recovery amount and waste heat utilization amount are generally set to be the same; when the waste heat recovery amount is greater than the waste heat utilization amount, the excess Q f，c -Q f，d The heat is taken away by other cooling media to ensure that the temperature of the fourth storage device 44 is stable and the waste heat recovery system operates stably.

[0076] In addition, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present application will not further explain various possible combinations. In addition, the various different embodiments of the present application can also be combined arbitrarily, as long as they do not violate the idea of ​​the present application, they should also be regarded as the contents disclosed in the present application.

[0077] In the description of the present invention, it should be understood that the terms "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0078] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0079] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0080] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A compressed air energy storage system coupled with waste heat from a thermal power plant, characterized in that: include: An energy storage unit, the energy storage unit comprising a compression device and a gas storage device, the gas storage device being connected to an outlet side of the compression device; A turbine unit, the turbine unit being connected to the outlet side of the gas storage device and comprising a plurality of turbine structures; a first heat exchange unit, the first heat exchange unit comprising a first heat exchanger, at least one second heat exchanger, a first storage device and a second storage device, the first heat exchanger comprising a first flow path and a second flow path for mutual heat exchange, the first flow path being connected to the first storage device and the second storage device respectively, the second flow path being connected to the compression device and the gas storage device respectively, the second heat exchanger comprising a third flow path and a fourth flow path for mutual heat exchange, the third flow path being connected to the first storage device and the second storage device respectively, the fourth flow path being provided at the upstream side of at least one of the turbine structures so that the second heat exchanger is used to heat the airflow at the upstream side of the at least one turbine structure; The second heat exchange unit comprises a third heat exchanger, a fourth heat exchanger, a third storage device and a fourth storage device, the third heat exchanger comprises a fifth flow path and a sixth flow path for mutual heat exchange, the fifth flow path is respectively connected to the third storage device and the fourth storage device, the sixth flow path is respectively connected to the gas storage device and the turbine unit, so that the third heat exchanger is used to heat the airflow between the gas storage device and the turbine unit, the fourth heat exchanger comprises a seventh flow path and an eighth flow path for mutual heat exchange, the seventh flow path is respectively connected to the third storage device and the fourth storage device, and the eighth flow path is suitable for circulating waste heat medium of a thermal power plant.

2. The compressed air energy storage system coupled with waste heat from a thermal power plant according to claim 1 is characterized in that: The plurality of turbine structures are arranged in sequence along the air flow direction, and the upstream side of each turbine structure is respectively provided with a second heat exchanger.

3. The compressed air energy storage system coupled with waste heat from a thermal power plant according to claim 1 is characterized in that: The number of the turbine structures is three or more.

4. The compressed air energy storage system coupled with waste heat from a thermal power plant according to claim 1, characterized in that: Also includes: A switch valve is provided between the energy storage unit and the turbine unit to control the on-off between the energy storage unit and the turbine unit.

5. The compressed air energy storage system coupled with waste heat from a thermal power plant according to any one of claims 1 to 4, characterized in that: The second heat exchange unit further includes a supercharger, and the supercharger is used to pressurize the medium in the second heat exchange unit.

6. A control method for a compressed air energy storage system, characterized in that: The compressed air energy storage system is a compressed air energy storage system coupled with waste heat from a thermal power plant according to any one of claims 1 to 5, and the compressed air energy storage system has a first working mode and a second working mode. In the first working mode, the energy storage unit and the first heat exchange unit are both in operation, the turbine unit is not in operation, and the third heat exchanger is not in operation; In the second working mode, the energy storage unit, the first heat exchange unit and the turbine unit are all in operation, and the third heat exchanger is in operation.

7. The control method of the compressed air energy storage system according to claim 6, characterized in that: The first storage device and the second storage device contain heat transfer oil, and the third storage device and the fourth storage device contain water. In the second working mode, the temperature of the water in the third storage device is T1, the temperature of the water in the fourth storage device is T2, and the fourth heat exchanger heats the air flow out of the air storage device to a preset temperature T3, T1<T3<T2<100℃.

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